#include<iostream>
using namespace std;
const int N = 510;
int f[N][N], w[N][N];
int n;
int main()
{
	cin >> n;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= i; j++) {
			cin >> w[i][j];
		}
	}
	for (int i = 1; i <= n; i++)f[n][i] = w[n][i];
	for (int i = n - 1; i; i--) {
		for (int j = 1; j <= i; j++) {
			f[i][j] = max(f[i + 1][j], f[i + 1][j + 1]) + w[i][j];
		}
	}
	cout << f[1][1] << endl;
	return 0;
}